Technology for cutting a quadrangular base material having a relatively large size to manufacture a plurality of quadrangular unit pieces having relatively small sizes has been adopted in various fields. For example, a base material sheet having a predetermined width and a long length may be repeatedly cut using a cutter frame having a plurality of cutters mounted therein to simultaneously manufacture a plurality of quadrangular unit pieces though a one-time cutting process.
The cut quadrangular unit pieces may be subjected to an inspection process to check if any of the quadrangular unit pieces are defective. The quadrangular unit pieces found to be defective during the inspection process are sorted as defective products. If a large number of quadrangular unit pieces are found to be defective, material loss is serious.
Defects of the cut quadrangular unit pieces mainly originate in a quadrangular base material (also referred to as a base fabric sheet). Generally, a base fabric sheet may be manufactured by extruding and stretching a predetermined material. The base fabric sheet is very long, and therefore, the base fabric sheet is wound on a roller such that the base fabric sheet is easily handled at the extruding process, at the stretching process, and at a subsequent cutting process. At the stretching process, the base fabric sheet is stretched while opposite ends of the sheet are fixed to a predetermined stretching device, with the result that end regions of the base fabric sheet may be defective. At the winding process, the end region of the base fabric sheet fixed to the roller may be defective. Also, if the roller has scratches, periodic defects may occur at the base fabric sheet contacting the roller during the rotation of the roller.
In a case in which quadrangular unit pieces are cut from a base fabric sheet having such defects, defective quadrangular unit pieces may be disposed of, and therefore, manufacturing costs may be increased.
There is known technology relating to apparatuses for manufacturing quadrangular unit pieces that are capable of reducing defects of the quadrangular unit pieces to solve the above problems.
As an example of such technology, there is known technology for checking whether a quadrangular unit piece slit in the longitudinal direction is defective using an inspection unit and, upon checking that the quadrangular unit piece is defective, transferring the defective quadrangular unit piece to a cutting unit to cut and remove the defective quadrangular unit piece. In this technology, however, a large amount of scrap is produced. When quadrangular unit pieces are successively arranged, process continuity is seriously deteriorated. Also, when quadrangular unit pieces having various sizes are simultaneously cut from a base material and/or the quadrangular unit pieces are cut from the base material at a predetermined inclination, as will be described hereinafter, practical applicability may be substantially difficult.
Specifically, the size (width) of the base material is specified, whereas the size of the quadrangular unit pieces may vary as needed, due to various factors, such as the limitation of base material suppliers, the efficiency aspect of the manufacturing process, and the fluctuation in demand of the quadrangular unit pieces. In this case, the cutting efficiency greatly varies depending upon in which structure the cutter frame is configured, i.e., in which structure cutters for cutting the quadrangular unit pieces from the base material are arranged, when cutting a plurality of desired quadrangular unit pieces based on the size of the base material. The low cutting efficiency increases the amount of scrap, produced from the base material, which will be disposed of after the cutting process, with the result that eventually, the manufacturing costs of the quadrangular unit pieces are increased.
When the size (width and length) of a base material is in constant proportion to the size (lateral length and longitudinal length) of specific quadrangular unit pieces, it is possible to minimize a cutting loss rate by sequentially arranging the quadrangular unit pieces such that the quadrangular unit pieces are brought into contact with one another at positions having such constant proportion. However, when such constant proportion is not formed, the cutting loss rate may vary depending upon the array structure of the quadrangular unit pieces. Furthermore, when the quadrangular unit pieces are to be cut at a predetermined angle to the longitudinal direction of the base material, a large amount of scrap is inevitably produced.
An example of a process of arranging quadrangular unit pieces on an imaginary frame at a predetermined inclination is illustrated in FIG. 1. Specifically, FIG. 1 illustrates a process of locating quadrangular unit pieces having a relatively small size at an imaginary quadrangular coordinate system corresponding to a cutting frame which cuts the quadrangular unit pieces from the base material to set the arrangement of cutters in the cutting frame.
Referring to FIG. 1, quadrangular unit pieces 20 are inclined at an angle of 45 degrees in an imaginary quadrangular coordinate system 10 of a cutting frame. The number of cases in which the quadrangular unit pieces 20 are arranged in the imaginary quadrangular coordinate system 10 without overlap may be large. For example, the position of a first quadrangular unit piece 20 may be specified, and then the position of a second quadrangular unit piece 21 may be set. The same process may be repetitively carried out with respect to a plurality of quadrangular unit pieces including a third quadrangular unit piece 22.
It is generally preferable to arrange the quadrangular unit pieces 20, 21 and 22 such that the quadrangular unit pieces 20, 21 and 22 are adjacent to one another to manufacture a cutting frame having a high cutting rate (or a low cutting loss rate). For example, the first quadrangular unit piece 20 may be located such that two vertices of the first quadrangular unit piece 20 contact the outer circumference of the imaginary quadrangular coordinate system 10. In this state, the second quadrangular unit piece 21 may be located at various positions such that the second quadrangular unit piece 21 contacts one side of the first quadrangular unit piece 20. In the same manner, the third quadrangular unit piece 22 may be located at various positions such that the second quadrangular unit piece 21 contacts one side of the first quadrangular unit piece 20 and/or the second quadrangular unit piece 21 after the location of the second quadrangular unit piece 21. This process is repetitively carried out with respect to a maximum number of quadrangular unit pieces 20, 21 and 22 under a condition in which the quadrangular unit pieces 20, 21 and 22 are included in the imaginary quadrangular coordinate system 10.
Although an array structure having the maximum cutting rate is obtained through the above process, however, a plurality of defective quadrangular unit pieces may be obtained due to defects of the quadrangular unit pieces when the quadrangular unit pieces are cut to produce real products.
Consequently, there is a high necessity for technology relating to a method of manufacturing quadrangular unit pieces that is capable of efficiently calculating the number of cases in which good-quality products can be manufactured to reduce a defect rate of products at a continuous mass production process and reducing a defect rate of products even when cutting the quadrangular unit pieces from a base material at a predetermined inclination, thereby preventing waste and reducing manufacturing costs of the quadrangular unit pieces.